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排序方式: 共有793条查询结果,搜索用时 46 毫秒
731.
Naonari Sakamoto Yutaro Hirai Tsunenobu Onodera Takuma Dezawa Yutaka Shibata Hitoshi Kasai Hidetoshi Oikawa Hiroshi Yabu 《Particle & Particle Systems Characterization》2019,36(1)
Janus particles, particles that have two distinct aspects on their surface or interiors, have attracted much attention due to their potential for application. For the application of Janus particles to high‐resolution displays, and as light sources for optical circuits and fluorescent probes, the Janus particles should be nanosize to ensure high‐resolution display and analysis, responsive to external stimuli, and highly fluorescent. However, it is still a challenging issue to develop such highly fluorescent nanoscale Janus particles and control their alignment. Magnetoresponsive Janus particles, of which the orientation can be controlled by an external magnetic field, are prepared by the simple introduction of polymer‐coated magnetic nanoparticles (NPs) into the hemispheres of Janus particles. If these magnetoresponsive Janus particles can be combined with a strong fluorescence system, then they could be ideal candidates as components of the previously mentioned applications. In the present study, Janus particles are prepared with a fluorescent dye and gold nanoparticles (Au NPs) on one side. The optical properties of the resulting particles are assessed and discussed. Furthermore, the response of composite Janus particles containing dyes, Au NPs, and iron oxide NPs to an external magnetic field is discussed. 相似文献
732.
Cr-Si binary oxide prepared by a sol-gel method, when activated by visible light, catalyses highly selective oxidation of cyclohexane to cyclohexanone with molecular oxygen. 相似文献
733.
Dihydropyrimidine dehydrogenase (DHPDase), dihydropyrimidinase (DHPase) and beta-ureidopropionase (betaUPase) are the enzymes that catalyze the first, second, and third steps of the degradation of pyrimidines, respectively. beta-Ureidopropionate (betaUP) and beta-ureidoisobutyrate (betaUIB) are increased in the urine of patients with betaUPase deficiency. The original case in which betaUPase deficiency was discovered by NMR spectroscopy was an 11-month-old patient who presented with hypotonia and dystonic movement. We detected a second but asymptomatic case during a pilot study of neonatal screening with filter-paper urine, urease pretreatment and gas chromatography/mass spectrometry (GC/MS). The urease pretreatment of urine without fractionation resulted in a high recovery of these polar ureide compounds and allowed the highly sensitive GC/MS detection and diagnosis of betaUPase deficiency. betaUP and betaUIB were identified using GC/MS techniques. In the urine of the neonate with betaUPase deficiency, betaUP and betaUIB were persistently increased. Thymine, 5,6-dihydrothymine and 5,6-dihydrouracil were increased only moderately but significantly. It is known that thymine and uracil increase markedly in DHPDase deficiency, and 5,6-dihydrothymine and 5,6-dihydrouracil increase in DHPase deficiency. Therefore, betaUPase deficiency can be differentially diagnosed from the first and second enzyme deficiencies. Application of this specific and sensitive diagnostic procedure will lead to an understanding of the clinical heterogeneity of betaUPase deficiency. Furthermore, the identification of patients with defects in pyrimidine metabolism will enable doctors to avoid cancer chemotherapy with pyrimidine analogues such as 5-fluorouracil, which could be dangerous for these patients. 相似文献
734.
Hiroshi Hirai 《Annals of Combinatorics》2006,10(1):111-128
A characterization is given to the distance between subtrees of a tree defined as the shortest path length between subtrees.
This is a generalization of the four-point condition for tree metrics. For this, we use the theory of the tight span and obtain
an extension of the famous result by Dress that a metric is a tree metric if and only if its tight span is a tree.
Received July 13, 2004 相似文献
735.
Regioselective formation of N-arylmethylimidazoles and C-arylimines was found in the reaction of 4,5-diamino-2,1,3-benzothiadiazole with selected aromatic aldehydes. The regiochemistry of the reaction products was confirmed by single crystal X-ray analysis. Gibbs free energy calculation using DFT method at the B3LYP/6-31G(d) level supports the regio-selectivity observed. The 4-imine obtained in the reaction of 4,5-diamino-2,1,3-benzothiadiazole with pyrene-1-carboxaldehyde showed an unusually low magnetic field shift of the imine proton that was reproduced by molecular calculations. 相似文献
736.
T. Nagatomo K. Matsuta Y. Nakashima T. Sumikama M. Ogura K. Akutsu T. Iwakoshi H. Fujiwara T. Minamisono M. Fukuda M. Mihara T. Miyake K. Minamisono S. Momota Y. Nojiri A. Kitagawa M. Sasaki M. Torikoshi M. Kanazawa M. Suda M. Hirai S. Sato S. Y. Zhu J. Z. Zhu Y. J. Xu Y. N. Zheng J. R. Alonso G. F. Krebs T. M. Symons 《Hyperfine Interactions》2004,159(1-4):273-276
The momentum dependences of the nuclear spin polarization P and alignment A of 13B(, T
1/2 = 17.36 ms) produced in the 100A MeV 15N + Be collisions have been measured by detecting β-ray asymmetry. Because both the P and A were significantly smaller than the prediction from a simple kinematical model, some relaxation mechanisms must be take into
account. Comparing the signs of the observed alignment of 12B, the sign of the quadrupole coupling constant eqQ of 13B in TiO2 was determined to be positive. 相似文献
737.
X.?P.?Zhu Tomiyuki?Yukawa Takehiro?Kishi Makoto?Hirai Hisayuki?Suematsu Weihua?Jiang Kiyoshi?YatsuiEmail author 《Journal of nanoparticle research》2005,7(6):669-673
Synthesis of photoluminescent Si nanoparticles has been successfully prepared using an intense pulsed ion-beam evaporation
(IBE) technique in vacuum. Si nanoparticles are produced by the IBE method without any post-annealings. Photoluminescence
(PL) mainly in blue range with a peak of 455 nm and a shoulder near 510 nm is observed in as-deposited Si nanoparticles at
room temperature. The blue light emission is relatively stable with no noticeable change, as the samples have already stored
in air more than 4 months. The observed PL does not fit the quantum confinement model, since a majority of particle size is
around ~20 nm, estimated by SEM and XRD measurements. Moreover, hydrofluoric acid (HF) corrosion tests on the Si nanoparticles
also indicate a correlation between the presence of the surface oxide layers and the PL. Oxide-related luminescence is likely
the source of this blue light emission. 相似文献
738.
Glycosides of Atractylodes ovata 总被引:3,自引:0,他引:3
Kitajima J Kamoshita A Ishikawa T Takano A Fukuda T Isoda S Ida Y 《Chemical & pharmaceutical bulletin》2003,51(9):1106-1108
A new coumarin glycoside and a new glycoside of an acetylene derivative were isolated from the water-soluble portion of the methanolic extract of Atractylodes ovata rhizome together with eight known compounds. Their structures were characterized as scopoletin beta-D-xylopyranosyl-(1-->6)-beta-D-glucopyranoside and (2E)-2-decene-4,6-diyne-1,8-diol 8-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside, respectively, based on chemical and spectroscopic investigations. A comparison of the polar constituents among Atractylodes japonica, Atractylodes lancea, and A. ovata is led to the conclusion that A. ovata is distinguishable from A. lancea and A. japonica, as also shown by phylogenetic analysis. 相似文献
739.
[reaction: see text] Photoirradiation of benzene solutions containing 1-diarylvinylidene-2,2,3,3-tetramethylcyclopropanes (2a--d) afforded rearranged products 1,2,3-butatrienes (3a-d) in good to high yields. Photorearrangement from 2,2,3-trimethyl and 2,2- and 2,3-dimethyl derivatives 2e--g also proceeded, but the rates of the rearrangement were lower than those of 2a--d. A singlet mechanism is proposed for this photorearrangement, where alkyl migration occurs from 1,3-biradical intermediates generated via the homolysis of the C1-C2 bond. Generation of diarylvinylidene carbenes from 1,3-biradicals might be competitive with the formation of 3. 相似文献
740.
Substitution reactions between samples and colored metal complexes, such as magnesium-methylthymol blue and cerium(III)-xylenol orange, are applied to flow injection determinations of orthophosphate, diphosphate, triphosphate and EDTA. Various types of manifold with a stopped-flow device are used; the importance of addition of reagents in a logical sequence is stressed. Kinetic and thermodynamic factors associated with the substitution reactions were found to be significantly reflected in the f.i.a. profiles and stopped-flow signals. The working ranges of the methods are 10-5–10-4 M. 相似文献